The invention relates generally to audio sampling rate conversion systems and more particularly to audio sampling rate conversion systems that convert multiple streams of different rate audio.
Proposed multimedia computer standards such as Intel Corporation's AC-97 recommended standard and Intel Audio '98 Roadmap and Recommendations industry review drafts describe various desired audio subsystems for multimedia computer systems. Such proposals seek PC computer audio systems that can mix and process audio streams from numerous audio sources sampled at many different sampling rates.
When different audio streams are sampled at different rates, desirable mixing of the streams requires that the samples be converted to a common rate so that a common number of samples exist for each stream. For example, if audio from one source, such as a compact disc (CD) or digital versatile disc (DVD) is sampled at a first rate and needs to be mixed with audio sampled at a different rate from another source, such as a stored computer audio file, the audio must undergo rate conversion to be mixed by a mixer such as a digital signal processor. Also, where all audio is output through speakers coupled through the computer, the digital to analog converters for outputting analog audio for the speaker require a common sampling rate such as 48 kilosamples per second (Kss). All audio streams from all differing sources must be converted to be suitably output by the speaker drivers. In addition, real time conversion would allow mixing of real time audio input such as live audio from a modem, TV tuner or other source. Also, when performing the audio rate conversion and mixing operations on multiple audio streams, it is desirable to isolate the processing from a host PC processor to allow the host processor additional capacity to perform other functions.
Therefore, there exists a need for an audio sampling rate conversion system and method that facilitates conversion of multiple streams of different rate audio and facilitates reducing host processor intervention during rate conversion. Such a system should also facilitate mixing of the differing rate audio streams.